1. Field of the Invention
The present invention discloses new bioabsorbable staples, new delivery systems for the application of the bioabsorbable staples and new methods for tissue closure. These bioabsorbable staples improve the consistency and reliability of the suturing process, and facilitate the wound closure process.
The first type of bioabsorbable staple is comprised of a single piece. The one-piece staple has three parts, namely, an elongated body, a retainer at one end of the elongated body, and an arrow head or connector head at the other end of the elongated body. The retainer has a tunnel passing through its core. The arrow head or connector head is inserted through the tunnel of the retainer and forms a secure lock with the retainer. The secured arrow head or connector head, retainer and elongated body form a closed ellipsoid suture structure.
The other type of bioabsorbable staple is comprised of two pieces. The two-piece staple or suture is comprised of a first elongated body having a leg connected to an arrow head at each end and a second elongated body having a retainer at each end, where each retainer contains an eyelet. The arrow heads are separately inserted into the eyelets of the retainers. The secured arrow heads, retainers and elongated bodies form a closed ellipsoid suture structure.
The staples are delivered through a separate staple delivery device. The first type of delivery device is a manually powered instrument for applying one bioabsorbable staple at a time. The second type of delivery device is semi-automatic for applying one or more bioabsorbable staples.
2. Description of the Related Art
Because of the advantages over conventional suturing techniques, mechanical stapling is now widely used in surgical procedures. Wound closure with stainless steel staples has resulted, for example, in decreased tissue trauma, a reduction in the length of hospital stay, and a lower infection rate (see, for example, Steckel et al., Experimental Evaluation of Absorbable Copolymer Staples for Hysterectomy, Obstetrics & Gynecology, Vol. 68, No. 3, pp. 404-410, September 1986).
Numerous types of surgical staples have been reported. For example, U.S. Pat. No. 3,625,220 (Engelsher) discloses a suture guard device comprised of an outer tube, an inner tube, and a locking means. The suture guard is semirigid and preferably made of polyethylene.
U.S. Pat. No. 4,534,350 (Golden et al.) discloses a two-piece tissue fastener comprised of an open loop fastening member having two legs with rows of rounded protrusions and a receiver. The legs of the fastening member are inserted into bores of the receiver and the rounded protrusions cooperate with a bore to form a secure connection.
Both U.S. Pat. No. 4,950,285 (Wilk) and U.S. Pat. No. 5,123,913 (Wilk et al.) disclose a one-piece suture device comprised of:
a) a thread provided with a series of resilient projections along a portion of its length,
b) a loop defining an opening,
c) a joining means for connecting one end of the thread to the loop, and
d) locking means.
U.S. Pat. No. 5,601,604 (Vincent) discloses a one-piece gastric band comprised of a body portion with a tail end and a buckle. The tail end of the body portion is inserted into the buckle to form a loop.
However, none of these patents disclose bioabsorbable staples and all are patentably distinguishable over the bioabsorbable staples of the present invention. Furthermore, none of these patents is believed to have any direct relevance to the patentability of the bioabsorbable staples of the present invention.
Although the advantages of stapling are numerous, complications associated with the use of steel staples led to the development of bioabsorbable staples.
Bioabsorbable staples were developed by combining different concentrations of lactide and glycolide, polymerized under varying conditions to enhance their rate of hydrolysis and absorption from tissues. In the early 1980s, lactomer absorbable plastic staples, e.g., polysorb, became available for use in hysterectomy in women. Lactomer staples are hard and opaque, and are unlike conventional metallic staples in that they are not bent during their application to form the shape of a "B". Rather, each copolymer staple is composed of two parts: a "U"-shaped fastener and an "8"-shaped retainer. When the stapling instrument is fired, the fastener is forced through the tissue and locks into its retainer. Currently available lactomer staples retain about 75% of their initial strength during the first postoperative week, with 40% tensile strength retention at about 2 weeks. The staples begin fragmenting after 3 to 4 weeks, and absorption follows.
Numerous types of bioabsorbable surgical staples have been reported. For example, U.S. Pat. No. 4,534,352 (Korthoff) discloses a two-piece surgical fastener made from an absorbable resinous material. The surgical fastener is comprised of a base and a prong-containing member. Each prong is inserted into an aperture in the base to form a secure connection.
U.S. Pat. No. 4,612,923 (Kronenthal) discloses a two-piece surgical fastener made from a synthetic absorbable polymer containing an absorbable glass filler. The surgical fastener is comprised of a staple and a receiver. The staple is inserted into openings in the receiver to form a secure connection.
U.S. Pat. No. 4,646,741 (Smith) discloses a two-piece surgical staple made from a blend of a lactide/glycolide copolymer and poly(p-dioxanone). The surgical staple is comprised of a base with two legs and a receiver. The legs of the base are inserted into receptacles in the receiver to form a secure connection.
U.S. Pat. No. 4,889,119 (Jamiolkowski et al.) discloses a two-piece surgical fastener made from a glycolide-rich blend of two or more polymers. The surgical fastener is comprised of a base with two legs and a receiver. The legs of the base are inserted into receptacles in the receiver to form a secure connection.
U.S. Pat. No. 5,282,829 (Hermes) discloses a two-piece biodegradable surgical device comprised of a fastener with two prongs and a receiver. The prongs of the fastener are inserted into the receiver to form a secure connection. Both the fastener and the receiver contain a hollow core region.
U.S. Pat. No. 5,439,479 (Shichman et al.) discloses a biodegradable two-piece surgical clip comprised of a fastener and a retainer. The fastener has a set of legs containing gripping means adapted to be engaged by the retainer. When the legs of the fastener are engaged by the retainer, a closed connection is formed.
U.S. Pat. No. 5,462,542 (Alesi, Jr.) discloses a biodegradable one-piece surgical strap assembly having a flexible elongated strap and a buckle attached to one end of the strap. A portion of the strap contains a plurality of ratchet teeth. The ratchet teeth of the strap engage a locking mechanism in the buckle to form a loop.
U.S. Pat. No. 5,549,619 (Peters et al.) discloses a biodegradable one-piece or two-piece surgical device comprised of an eye with a latching pawl and a flexible strip with ratchet teeth. The ratchet teeth of the flexible strip engage with the latching pawl of the eye to form a loop.
U.S. Pat. No. 5,643,295 (Yoon) discloses an apparatus for suturing tissue comprised of a knotting element connected between two length portions of filamentous suture material to form a contractile loop for confining segments of the length portions therein.
However, each of these patents is patentably distinguishable over the bioabsorbable staples of the present invention and none of these patents is believed to have any direct relevance to the patentability of the bioabsorbable staples of the present invention.
Likewise, numerous types of surgical staple delivery systems have been reported. For example, U.S. Pat. No. 3,949,924 (Green) discloses a manually powered surgical stapling instrument for stapling together skin or fascia. The instrument has a main body with a nose portion that has means for advancing and forming staples around an anvil.
U.S. Pat. No. 4,204,623 (Green) discloses a manually powered surgical stapling instrument for applying sterilized staples to disunited skin or fascia. A pusher is slidably mounted in the cartridge for advancing the stales, for ejecting the staples and for forming the staples around an anvil.
U.S. Pat. No. 4,489,875 (Crawford et al.) discloses an instrument for applying staples to skin by bending the staple around an anvil. As the staple is forced against the anvil, the staple bends and the legs penetrate the tissue and apply closing pressure across the wound.
However, each of these patents is patentably distinguishable over the bioabsorbable staple delivery systems of the present invention and none of these patents is believed to have any direct relevance to the patentability of the delivery systems of the present invention.
A thorough review of the field of bioabsorbable staples and stapling instrumentation has been reported by Michael M. Pavletic and Anthony Schwartz in Veterinary Clinics of North America: Small Animal Practice, Volume 24, Number 2, pages 247-278, March 1994, and by Chih-Chang Chu, Anthony von Fraunhofer and Howard Greisler, "Wound Closure Biomaterials and Devices", CRC Press, Inc., 1997.